This application claims the priority benefit of Taiwan application serial no. 90111126, filed May 10, 2001.
1. Field of Invention
This invention relates to a fabrication method for a semiconductor device. More particularly, the present invention relates to a method for cleaning a semiconductor wafer.
2. Description of Related Art
In the fabrication process of integrated-circuit devices, wafer cleaning is the most frequent performed processing step. The purpose of wafer cleaning is to remove the organic compound, the metal crud or particulate that is attached to the surface of the wafer. These contaminants greatly affect the subsequent process and the quality of the product. The metal crud contaminant would lead to a current leakage at the p-n junction, a reduction of the lifetime of some carriers and a reduction of the breakdown voltage of the gate oxide layer. The attachment of particulate to the surface of a wafer would definitely affect the accuracy of pattern transferring in a photolithography process. It may even lead to a short circuit. The wafer cleaning process, therefore, must be able to effectively remove the organic compound, the metal crud and particulate. Moreover, a formation of a native oxide layer on the wafer surface after the cleaning process has to be prevented to minimize the surface roughness.
The current industry employs the RCA cleaning process to clean the semiconductor wafer. Referring to FIG. 1, FIG. 1 is a flow diagram, illustrating the basic steps in the RCA cleaning process.
Step 101: Cleaning the wafer using an aqueous solution of a sulfuric acid/hydrogen peroxide mixture (SPM) to remove, for example, the photoresist residue or particulate type of organic contaminant that remains on the wafer surface.
Step 102: Performing a quick-dump rinse (QDR) process by using a large quantity of deionized water to clean the wafer surface and to remove the SPM cleaning solution that remains on the wafer surface.
Step 103: Performing a SC1 cleaning process using the SC1 cleaning solution (NH4OH/H2O2/H2O=1:1:5), also known as APM, at a temperature of 75 degrees Celsius to 85 degrees Celsius to clean the wafer and to remove the organic compound and particulate that attache to the wafer surface.
Step 104: Performing a quick-dump rinse (QDR) process by using a large quantity of deionized water to clean the wafer surface and to remove the SC1 cleaning solution that remains on the wafer surface.
Step 105: Performing a SC2 cleaning process using the SC2 cleaning solution (HCl/H2O2/H2O=1:1:6), also known as HPM, at a temperature of 75 degrees Celsius to 85 degrees Celsius to clean the wafer and to remove the metal crud that attaches to the wafer surface.
Step 106: Performing a quick-dump rinse (QDR) process by using a large quantity of deionized water to clean the wafer surface and to remove the SC2 cleaning solution that remains on the wafer surface.
Step 107: Performing a dilute hydrofluoric acid (DHF) cleaning process by placing the wafer in a dilute hydrofluoric acid aqueous solution (HF/H2O=1:99) to remove the native oxide layer on the wafer.
Step 108: Performing a quick-dump rinse (QDR) process by using a large quantity of deionized water to clean the wafer surface and to remove the DHF cleaning solution that remains on the wafer surface.
Step 109: Performing a rinsing process by placing the wafer into the final rinse (FR) tank to further clean the wafer.
Step 110: Performing a drying process by placing the wafer in a drying station, for example, in an isopropyl alcohol (IPA) station using the IPA vapor to remove the moisture on the wafer and to dry wafer.
After the completion of the cleaning processes 101, 103 and 105 in the above RCA process, a quick-dump rinse process is performed using deionized water to sufficiently clean the wafer in order to prevent the SPM, the SC1 and the SC2 cleaning solution to remain on the wafer surface. The SPM cleaning solution, however, is very viscous and is very difficult to remove. Furthermore, the SPM cleaning solution that remains on the wafer easily forms crystal when it comes in contact with air. Therefore, in order to remove the SPM cleaning solution residue, a huge quantity of deionized water is required in the subsequent quick-dump rinse process to completely remove the SPM cleaning solution residue.
The present invention provides a semiconductor wafer cleaning method, wherein after the chemical cleaning process and before the quick-dump rinse process, an acid-base neutralizing step is performed. Using various diluted acid solution and basic solution to neutralize the pH value of the wafer surface, the quantity of deionized water used in the quick-dump rinse process is thus reduced. As a result, the manufacturing cost is reduced and the efficiency of the process is increased.
The present invention provides a cleaning method for a semiconductor wafer, wherein subsequent to the chemical cleaning of the wafer, a neutralizer is added to a chemical cleaning tank that fills with deionized water, to neutralize the pH of the wafer surface. Thereafter, a quick-dump rinse process is conducted to remove the chemical cleaning solution debris on the wafer surface.
The invention provides a wafer cleaning method, wherein subsequent to the chemical cleaning process and before the quick-dump rinse process, a neutralizer is added to a tank of deionized water such that the wafer surface is neutralized to a neutral pH value. The quantity of deionized water used in the subsequent quick-dump rinse process is thus reduced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.